Machine-switching telephone system



C; L. GOODRUM. MACHINE SWITCHING TELEPHONE SYSTEM.

7 I APPLICATION FILED OCT. 31,1919- 1,396,741 Patented Nay. 15, 1921.

, //71//770/ Char/es 1.. Good/am UNITED STATES-,2

PATENTS-OFFICE.

cnmns L. menu, or You, u. 1., ASSIGHOBY to warm morale comm, moonrou'mm yor nnw You, x. 2., A comes-non ormlw To all whom it may concern Be it known that I, CHAR nsL. GoonRUM, a citizen of the United States, resldmg at New'York in the county of New York and State of New York, have invented certain new and useful Improvements in Machine- Switching Telephone Systems, of which the following is a full, clear, concise, and ex act description.

This invention relates to machine switching telephone systems and more particularly to trunking arrangements theretor.

It is the object of this invention to provide a simplified circuit arrangement for systems employing switches in which individual subscribers lines as well. as groups of trunk lines terminate, and in whicheither an individual line or an idle one of a desired 7 group of trunks may be selected.

A further object is the provision of controlling circuits for a switch of the character described in which no change in. the circuits of the switch is necessitated when it is desired to change the grouping of the lines terminating in the switch, rearrangement of the mechanism of'the switch bank being all that is required.

' In accordance with these objects, an auxiliary contact is provided for the switch. and is so positioned in relation to one of the brushes of the switch that aslight extra movement of said brush, beyond that caused by engagement with an individual line terminal, will move said brush into engagement with the auxiliary contact, thereby completing a connection between the termi: nal engaged and both the brush and auxil iary contact. This contact closing movement of the brush, in the present embodiment, is caused by superposing'any metallic substance on the contacting face of the terminal which it is desired to have effect such movement. Controlling circuits fora stepby-step connector switch are arranged so that when the brushes are set on a set of individual line terminals or on an idle set I of trunk terminals, one of which has been prepared in accordance with this invention, no hunting results. If, however, the brushes are set'on a busy set of prepared trunk terminals, hunting is initiated and continued until either an idle or the last set of trunk terminals is encountered by the brushes, at which time the switch stops. If such trunk is idle, connection is made there- Specification of Letters Patent.

IAOHINE-BWITCKIIG TELEPHONE SYSTEM Patented 'Nov. 15, 1921.

Application filed omm' a1, 1919. Serial no. 334,101.

to; if not, a busy tone is transmitted to the callin party. i

Re erring to the accompanying drawings, Figure 1 shows the circuits employed in completing a connection from a calling to a called line; Fig. 2 is a erspective view of a brush set and terminal bank of a connector switch, certain of'whose terminals have been prepared in accordance with this invention; and Fig. 3 is a detailed view of two terminals in such a bank.

Referring now to Fig. 2, brushes 21, 23 and 24 and auxiliary contact 22 are mounted on a rotatable brush shaft 25, being in sulated therefrom and from each other in any desired manner. When the brushes rest on terminals 26, 27 and 28, the contact between brush 21 and auxiliary spring 22 is open, but when brush 21 rests on a terminal 29, upon which has been placed a metallic sleeve 31, the upward pressure of this sleeve on the end of the brush raises this brush sufiiciently to close the contact 30 between the brush and its auxiliary spring 22. The structure of the sleeve 31' is clearly shown in Fig. 3. The means shown for closing contact 30 consists of a metallic sleeve having a cylindrical upper surface, and projections 33 and 34 by which it .grips the terminal 29. It is to beunderstood, however, that any suitable attachment might be made to terminal 29 to close contact 30 when brush 21 is in engagement with a terminal so prepared, or terminal 29 might be formed with a cylindrical contact face to effect closure of contact 30.

It is believed that the invention will be more readily understood from a descrip tion ofthe operation of the system, which is as follows When the subscriber at substation 1 desires to make a call, he removeshis receiver from its hook (not shown) thereby operating a line finder switch, of. which only the brushes 3, 4c, and 5 are shown, to seize the terminals of the calling line. The sub scriber then dials the hundreds digit of the wanted line on his impulse sender 2, to operate the first selector switch, of which only the brushes 6, 7 and 8 and their associated terminals are shown. When the selector brushes 6 and 7 engage the terminals associated with an idletrunk circuit of which the conductors, 9 and 10, lead to a connector switch, they complete a circuit from placed on. the test conductor ground placed thereon by 13, closed until'after the first primary step forrelay' 11; Relay grounded battery through the right-hand winding of relay 11, conductor 10, brush 7 and its associated terminal, brush 4 and its associated terminal, through the loop at substation 1, brushes 3 and 6 and their associated terminals, conductor 9 and left-hand winding of relay 11 to ground. Relay 11' energizes in this circuit, thereby completing an energizing circuit for relay 12. The subscriber now dials the. tens impulses of the wanted line, thereby interrupting the circuit 12 being slow to release, remains energized throughout this series of impulses and at its right hand armature applies busy ground potential ,to conductor and its associated terminal. This ground is 40 before the the preceding switch is removed. Upon the first retraction of the armature of relay 11, a circuit is completed from ound, armature and-back contact of relay 11, left-hand armature and front contact of relay 12, off-normal contact of the switch, through the winding, of slowrelease relay 14 and lPrimary magnet 15 to grounded battery. agnet 15 is energized in this circuit, thereby stepping the brushes 21, 23 and 24 onestep in their primary movement and opening contact 13. Relay 14 was also energlzed and remains energized for a short time after the opening of contact 13. If more than one impulse'is transmitted in the tens series, a circuit will be completed on the second and all subsequent retractions of the armature of relay 11, which may be traced from und, armature and back contact of relay 11, left-hand armature and front contact of relay' 12, offnormal contact 16, closed after the first primary step, armature and front contact of relay 14, through the windings of relay 14 and magnet 15 to ounded battery. Relay 14 is held energize in this circuit and magnet 15' steps the brushes to the desired level of the terminal bank. At the conclusion of this series of impulses, relay 11 retains its armature attracted and relay 14 denergizes. The subscriber now dials the units impulse. Upon the first retraction of the armature of relay 11, a circuit is completed from ground,

armature and back contact of relay 11, lefthand armature and front contact of relay 12, contact 16, armature and back contact of relay 14, normal contact and sprin 17 of relay 18, through the winding 0 relay 19, outermost left-hand armature and back contact of why 20, through the winding of secondary magnet 35 togrounded battery. Magnet 35 is energized in this circuit and moves the brushes 24, 23 and 21 into engagement with terminals 28, 27 and 26. 1 .Relay 19 is also energized and being slow to release maintains its armatures attracted between impulses. If more than one units impulse is hand armature and front contact 0 sent, a circuit will be completed upon the second and subsequent denergizations of relay 11, which may be traced from ground, armature and back contact of rela 11, lefti relay 12 contact 16, armature and back contact of relay 14, conductor 36', left-hand armature and front contact of rela 19, winding of said relay, outermost 1e -hand 'garmature and back contact of relay 20, through the winding of magnet 35 to grounded battery. Assuming that two units im ulses were sent, the brushes 24, 23 and 21 w1ll now be in engagement with terminals 36, 37 and 38. As terminal 38 is not equipped with a sleeve 31, contact 30 will be 0 11. If the selected line is idle, a circuit Wlll, upon the denergization of relay 19, be completed from grounded battery, relay 39, terminal 38, brush 21, outer righthand armature and back contact of relay 19, through the'right-hand winding of relay 20, back contact and inner right-hand armature of relay 18, right-hand armature and front contact of relay 12 to ound. Relays 20 and 39 are energized in t is circuit. Relay 20 completes a locking circuit for itself from grounded battery through its left-hand winding, front contact and innermost lefthand armature, conductors 40 and 41 to ground at the right-hand armature of relay 12. This groun is also connected over conductors 41 and 40, middle left-hand armature andfront contact of relay 20 and conductor 42, through brush 21 to provide busy potential for multiples of terminal 38 of other switches, to hold cut-off relay 39 energized, and to shunt the right-hand winding of relay 20, which relay, however, is held up by its locking circuit. Upon the ener 'zation of rela 20, a circuit was comp eted from groun back contact and outer lefthand armat re of relay 43, front contact and outer right-hand armature of relay 20,

brush 24, terminal 36, through the call bell (not shown) at the called substation, terminal 37, brush 23, inner right-hand armature and front contact of relay 20, inner lefthand armature and back contact of relay 43, through the left-hand winding of relay 43 to a source of ringing current. The called subscribers bell is rung in this-circuit but relay 43 is marginal and will not energize until the resistance of the ringing circuit is lowered when the called subscriber answers. At this time relay 43 attracts its armatures completing a locking circuit for itself, from grounded battery through its right-hand winding, front contact and armature, conductors 40 and 41 to ground at the righthand armature of relay 12. In attracting through the winding of cut-olf left-hand winding of relay 44, an

cuit'and restores the connector switch in the 1 and line through relay 11, and to the called line from the free pole-of battery throu h the from ground at the right-hand armature of relay 12, conductors 41 and 40, right-hand contact of relay 43 and through the right-hand winding of relay'44.

At the completion of the conversation when the calling subscriberreplaces his receiver on its hook, he interrupts the circuit.

of relay 11. Relay 12 de'e'nergizes shortly thereafter and a circuit is completed fromgrounded battery, through the winding of release, magnet 45, contact 46, back contact and left-hand armature of relay 12, back contact? and armature of relay 11 to ground. Therelease magnet is energized in this cirwell-known manner. Relay 12 in retracting its right-hand armature removes the ground potential from conductor 40 which has been holding up the line finder and first selector switches. These switches are thereu on releaized and the system is ready for t e next cal Assumin the line associated with the selected term1nals'36, 37 and 38 isbusy at the time that brushes 24,23 and 21 come to rest on said terminals, ground potential is presenton test terminal 38 and a circuit will be completed from said ground over brush 21, outer right-hand armature now attracted spring 47 of relay 19, armature and back contact of magnet 35, through the winding of relay 18 and magnet 45 t to grounded battery. Magnet 45 is marginal and. will not-energize in this circuit, but relay, 18 is energized and held up in this circuit until relay 19 retracts its armatures, at which time a substitute circuit is completed to Hold relay 18 energized, which may be traced from grounded battery through the windings of magnet 45 and re lay 18, back contact and armature of magnet 35, spring 47 of relay 19 and its normal contact, conductor 57, front contact and inner right-hand armature of relay 18, righthand armature and. front contact of relay 12 to'ground. Relay 18 in attracting its outer left-hand armature completes a circuit for the busy tone from ground, front contact and outer left-hand armature of relay 18, back contact and middle left-hand armature of relay 44, secondary winding of the busy tone source 48, conductor 49, through. the condenser, upper side of the line including brushes (Sand 3, through substation 1' and back over the lower side of the line, through the condenser and left-hand winding of relay 44 to grounded battery. The calling subscriber hearing this tone replaces his re ceiver on its hook and release of the connection takes place in the manner described.

ple of said terminal.

exchange shown as P. B. 11., he would have operated the connector switch to set brushes 24,23 ,and 21 on terminals 50, .51 and 52- of the firsttrunk in the group serving said exchange. Terminal 52 is .equipped with a sleeve 31 and closes contact 30 between brush 21 and spring 22. If the trunk circuit associated with these terminals is idle, battery potential, supplied through the winding of ut-oif relay 53 and terminal 52, will cause hand winding of re ay 20 over the circuit traced when terminals 36, 37 and 38 wereselected and found idle, and the call will be completed in the same manner as was described for that case. 4

If, however, the line represented by terminals 50, 51 and 52 is busy,ground potential will be present on terminal 52 and sleeve 31, being supplied from the, righthand armature of relay 12 of. the connector switch which is in enga ement with a multielay 18 is energized prior to the deenergization of relay 19, over acircuit which maybe traced from grounded battery throu h the winding of magnet 45, relay 18, bac contact and armature of magnet 35, spring 47 and outer right-hand armature of relay 19, conductor 42, brush 21, and bus test terminal 52 to ground as described. llpon, the deenergization of relay 19, a substitute holding circuit for relay 18 is completed over the circuit just traced as far as spring 47, thence over conductor 57, front contact and inner right-hand armature of relay 18 to ground at the righthand armature of relay 12. Relay 19, in retracting its inner right-hand armature, completes a circuit from grounded terminal 52, through brush 21, contact 30, spring 22, conductor 54, back contact and inner righthand armature of relay 19, through the resistance 55, spring 56 of relay 43, through the left-hand winding of relay 44 to grounded battery. Relay 44 is energized in this circuit and opens at its middle left-hand ar mature the busy tone circuit to prevent the calling subscriber from hearing a busy tone.

In attracting its right-hand armatures, relay 44 completes two locking circuits for itself, one operative when the brush 21 is centered on a busy terminal carrying a sleeve 31, and the other operative during the stepping movement of brush 21. These locking circuits may be traced from grounded battery, through the left-hand winding of relay 44, spring 56 and its normal Contact of relay 43, resistance 55, front contact and outer right-hand armature of relay 44, thence for the first circuit over conductor 61, brush 22, contact 30, brush 21 to ground on sleeve 31 of the busy terminal on which brush 2-1 rests; and for the second circuit through the inner right-hand armature and front contact of relay 44, front contact and he energization of the rightinner left-hand armature of relay .18 to round at the right-hand armature of rel ay 12. Relay 44, in attracting its inner left-hand armature,

- contact of relay'44, outer right-hand arma ture and spring 17 of relay 18, through the windingof relay 19, outermost left-hand armature and back contact of relay 20,

winding of magnet 35 to grounded battery.

Relay 19 is energized in this circuit but rela 18 does not denergize immediately since re ay 44 in attracting its outermost left-hand armature provided a Substitute circuit for relay 18. Magnet 35 is energized in series with relay 19 and steps brushes 24, 23 and 21 to terminals 58, 59 and 60. Attlie completion of this step, magnet 35 attracts its armature'to interrupt the holding circuit of relay 18 which denergizes to interrupt the circuit of magnet 35 and the second locking -circuit of relay 44. If terminals 58, 59 an "60 are those of an idle trunk circuit, battery from grounded battery,

potential will be present on terminal 60, and relay 44 becomes inert. Upon the deenergization of relay 19, which was energized in series with magnet 35, the previously traced circuit for the right-hand winding of relay .20 will be completed and ringing will take place as in the case when terminal 36, 37 and 38 were found idle. If, however, terminals 58, 59 and 60 are those of a busy trunk circuit,.ground potential being present on terminal 60, relay 44 will be maintained energized during the forward. step by its-second locking circuit and at the end of the step when brush 21 rests on sleeve 31 of terminal 60 by its first traced locking'circuit. Before relay l9 denergizes, an energizing circuit for relay 18 will be completed through the windings of magnet 45 and relay '18, back contact and armature of magnet 35, spring 47 and outer right-hand armature of relay 19, conductor 42, brush 21 toground on busy terminal 60.- Relay 18 in attracting its outer right-hand armature will complete the circuit previously traced from ground at the innermost left-hand armature of relay 44 for holding relay '19 energized and energizing magnet 35. Magnet 35 will step the brushes to the next set of terminals and in attracting its armature will open the circuit for relay 18. This cycle of operations will continue until an idle set of .terminals is found or until a test terminal not having a sleeve 31 is reached. If the first line, whose test terminal 62 is not equipped with a sleeve 31 is a busy line, contact 30 in opening will interrupt the locking circuit of relay 44, and the previously traced circuit for relay 18 will be completed. Relay 18 will complete the previously traced busy tone completes a circuit from ground, inner left-hand armature and front ,alent trunk lines, of a ready described. Should an idle set of terminals be found, or should the last set of terminals be idle, the switch would stop and the connection would be completed in the manner previously described.

Thus it appears, that by means of a simple metallic attachment, such as sleeve 31, which is easily removable from test terminals, trunk hunting many be brought about. All that is necessary to accomp ish this is to equip the test terminals of the trunks with sleeves 31. The last terminal in a group of trunk terminals, however, will not have such a sleeve in order to arrest the hunting movement. It is apparent that no change in the controlling circuits of the connector switch is necessitated when the number of trunks in a group is increased or decreased, or when terminals formerly assi ed to Individual subscribers lines are assigned to equivalent trunk circuits, the only change necessar being that of equipping all the test terminals, save the last in a grou of equivalent trunks, with sleeves 31. his system is adapted to any arrangement of roups of trunk terminals and individual lme terminals that may be desired, any number of groups of equivalent trunks may terminate in any level of the switch, and individual line terminals may be mixed indiscriminately between groups of trunk terminals.

at is claimed is:

1. In a machine switching telephone system, the combination with a group of equivnumber of individual telephone lines, a switch wherein said lines appear as sets of fixed terminals, one of the terminals in each set of trunk terminals being of a different form from the corresponding terminal of an individual line, a set of brushes for traveling over said terminals, an auxiliary contact closed by the setting of said brushes'on the terminals of a trunk line, and means responsive to the closure of said contact and the busy condition of the associated line for advancing the brushes to the next set of terminals.

2. In a machine switching telephone system, a plurality of groups of trunk lines, the lines in each group being equivalent, a plurality of individual telephone lines, a switch wherein said lines appear as sets of fixed terminals, the corresponding terminals of each group of equivalent trunks being arranged in a continuous row and the terminal sets of individual lines being interspersed between different groups of trunk terminals, one of the terminals in each set of trunk terminalssave the last set in its group being of different form from the corresponding terminal of an individual line, a set of brushes for traveling over said sets of terminals, an auxiliary contact closed by the setting of said brushes on any set of trunk terminals including one of said diflerently formed terminals, andmeans responsive to the closure of said contact and the busy condition of the line associated with the selected set of terminals for advancing the brushes to the next set of terminals.

3. In a machine switching telephone system, a calling line, called lines comprising a pluralit of groups of equivalent trunk lines and a p urality of individual tele hone lines, means for interconnecting sai lines including a switch wherein said called lines appear as sets of fixed terminals, one of the terminals in each set of trunk terminals save the last set in its group being of differentform from the corresponding terminal of an individual line, a set of brushes for traveling over said sets'of terminals, an auxiliary contact closed by the setting of said brushes on any set of trunk terminals containing oneof said differently formed terminals, means responsive to the closure of said contact and the busy condition of the trunk associated with the selected set of terminals for ste ping the brushes over the group of e' uiva ent terminals until either an idle or t e last'set of terminals in the group is reached,-means responsive to the nding of an idle line for completin the connection between said calling line an said idle called line, and means responsive to the busy condition of said last set of terminals 1n the group for stopping the switch a when the brushes are set thereon and transnumber of indiv mitting a busy tone to'said calling line.

4. In a machine switching tele hone sys tem, a group of equivalent trun lines, a i ual telephone lines, a switch wherein said lines a pear as sets of fixed terminals, a set of brus es for traveling over said sets of terminals, a metallic device applied to the test terminal of each set of vancing said brushes to r so trunk terminals, an auxilia contact closed by the setting ofsaid brus es on a set of 'trunk terminals whose test terminal carries said metallic device, and means res onsive to the closure of said contact and t e busy condition of the associated line for advancing the brushes to the next set of terminals.

5 In a machine switching telfiione system, "afgroup of uivalent tru lines, a number of indivi ual telephone lines, a switch wherein-said lines ap an as 'sets of fixed terminals, a sleeve slida le on said terminals carried by the test terminals of said trunk lines a set of brushes to travel over said sets, oi terminals, and means operated in to the setting of the test brush on a usy sleeve ca terminal for ad 0 next set of terminals.

set of terminals in said switch, a number of individual lines 6. In a machine switching telephone sys tem, a number of groups of trunk lines, the linesin each group being equivalent, a number. of individual telephone lines, a switch comprising sets of three fixed terminals arranged in rows, each of said sets of terminals representing an individual or a trunk line,

the'e uivalent trunk terminal sets in each group eing arranged in-a continuous row and the individual line terminal sets being interspersed indiscriminately between groups of trunk terminal sets, a set of brushes to travel over said terminal sets, and means responsive to the setting of said'brushes on the terminals of a busy trunk line for advancing said brushes to the terminals of the next equivalent trunk.

7. In a machine switching telephone system, a calling line, called lines comprising a brushes on the. busy first termina set of a group of equivalent trunk lines for advancing said brushes over said equivalent trunk line terminals until either an idle or the last oup is reached, means responsive to the nding of an idle line for com leting the connection between said calling hue and said idle calledline, and means responsive to the busy condition of the last set of trunk terminals in the group when the brushes are set-thereon for stopping the switch and transmitting a busy tone to said callin line. l

8. In a mac ine switching telephone 'sys-. tem wherein individual and trun pear as terminals in. the same automatic test terminals therefor, a number of trunk lines, test terminals therefor, sleeves mounted on certain of said trunk test terminals, and a controlling switch for said automatic switch 7 CHARLES L. GOODRUM. 

